The invention is in the field of computer data storage, and more particularly concerns the configuration of the head-disk-actuator (HDA) in a disk drive assembly within which a liquid lubricating material is circulated to provide a liquid bearing for spacing a head with respect to a rotating rigid disk at a very low flying height, to continuously clean the internal environment of the assembly, and to permit the use of a porous, open conical bearing for the spindle upon which the disk rotates.
As is known, prior art disk drive assemblies use a hub structure which supports a rotating rigid disk and is bearing-mounted within the enclosure structure of an HDA assembly. The orientation of the hub structure within the assembly is typically upright or cantilevered. In either case, the hub assembly is mounted for rotation on a rolling bearing assembly, usually of the ball bearing type. Such assemblies are well explained in Volume II of Magnetic Recording, edited by C. D. Mee et al., and published in 1988; see, in particular, pages 49-55.
In the prior art disk drive assembly, the internal environment is dry, and the bearings are integrally lubricated. In this regard, dessicated air is circulated in the assembly, while the bearings are packed with lubricant, assembled, and installed as integral units.
The air is circulated and filtered within the interior of the disk assembly in order to remove contaminating particles from the head-disk interface, which extends the life of the disk by reducing wear and tear of its surface. Conventionally, the air is circulated using either an open-loop or closed-loop air system.
Recently, dramatic reductions in the size of hard disk drive assemblies have been made. Assemblies which incorporate disks with diameters as small as 2.5 inches have been marketed. To date, all disk drive assemblies for hard disks utilize rolling bearing assemblies in the spindle mechanisms. In all disk sizes, ball and roller bearings form significant points of failure of the drive assembly. In the miniaturized disk drive assemblies, the small bearings are very susceptible to brinelling, a mode of failure whereby the stresses at the point contact of the balls within the bearing exceed the strength of the balls' steel, thereby initiating monotonic deterioration of the bearing. Relatedly, during manufacture, all hard disk drives are assembled on rubber cushions to provide suspension of the spindle assembly and its rolling bearings. The suspension is required since even minor impacts of the disk drive can destroy or significantly damage the bearings. When placed into a computer, a disk drive assembly is mounted on a mechanical suspension acting between the assembly and the chassis of the computer. This mechanical suspension is usually an integral part of the disk drive assembly; since the suspension is fixed in place, it forms the single most serious barrier to removeable disk drive assemblies.
In U.S. patent application Ser. No. 07/259,344, entitled "INFORMATION RECORDING APPARATUS WITH A LIQUID BEARING", filed Oct. 17, 1988, and commonly assigned with this application, the principle of a liquid bearing that supports the flight of a head on a rotating rigid disk was introduced. The unexpected result of using a liquid bearing is the provision of very low flying heights for the head with respect to the disk, and the concomitant increase in storage density. This worthy concept can provide benefits in personal computer technology, where miniaturization, ruggedness, and data compaction are significant goals. The challenge presented by use of a liquid bearing is to engineer a disk drive assembly environment in which the liquid forming the head-disk bearing is collected and recirculated to the head-disk interface after being thrown off the disk by the centrifugal force of the disk's rotation.
Unconstrained transfer of the liquid bearing material off of the disk during rotation establishes a "wet" environment in which the liquid material is free to circulate within the HDA assembly. Once the prospect of the wet environment is admitted, it provides opportunity for design elaborations that further improve the HDA for hostile environments. The liquid employed to form the liquid bearing is a low viscosity lubricating liquid with a high viscosity index that supports stable spacing of a head and rotating disk down to one microinch, or less.